Multi-decadal temperature changes and ocean heat content variability in the Southeastern Indian Ocean

Abstract

The Southeastern Indian Ocean features complex circulation patterns that modulate heat distribution. This study aims to investigate long-term temperature variability and Ocean Heat Content throughout the water column. Temperature changes were examined using the in situ and reanalysis products, covering the period 1960 to 2024, from the surface to 2,000 m. The results reveal that warming was 0.96 °C at 100 to 500 m, varying from 0.24 to 0.66 °C at 500 to 1,000 m. However, a slight cooling of −0.06 °C was observed at 1,000 to 2,000 m. Notably, OHC in the surface layer has increased by 0.01 to 0.02 °C per decade, reflecting substantial heat uptake. Key factors influencing these temperature changes include shifts in water mass sources and ocean current dynamics. At various observation stations, a clear upward trend in sea temperatures is observed, particularly between depths of 200 and 1,000 m. However, a cooling trend is observed at depths of 2,000 m. These findings underscore the ongoing impact of global warming, highlighting the complex and broad patterns of warming at varying depths. This study emphasises the importance of monitoring to mitigate the effects of climate change on this region, which has high marine biodiversity.